The proposed study will examine several possible mechanisms for the reduced risk of coronary heart disease observed in postmenopausal women receiving estrogen replacement in a placebo controlled, double-blind, randomized design. We will compare women receiving estrogen alone to those receiving placebo and to those receiving estrogen plus progesterone during the second half of the six month intervention. There is some evidence that the addition of progesterone will prevent or diminish estrogen related improvements in lipids and vascular tone. Therefore, the effects of each treatment regimen on lipid/lipoprotein profile, and vascular and lipid reactivity to stress will be assessed prior to treatment as well as after 3 and 6 months of the intervention. This proposal will fill an important gap in the literature by examining the effects of hormone replacement on hemodynamic and lipid reactivity to stress. In addition, we will examine the effects of hormone replacement therapy on symptoms of depression and anxiety through the use of structured interviews. Thus, we propose a multidisciplinary study of the costs and benefits of estrogen replacement on the psychological and cardiovascular health of postmenopausal women.